According to the control objectives, objects and requirements, NEWTEK applied programmable control (PLC) technology, adopted sequential control structure, established control model, and trial-produced a control system suitable for PSA series medical oxygen generators. According to the requirements of GJB2799-96 "General Specifications for Medical Molecular Sieve Oxygen Generators", basic parameter tests, performance and function tests and 48h continuous operation tests were carried out. The results showed that this control system realized the automation of the operation process of the oxygen generator, self-diagnosis and self-correction of faults, improved the reliability of the equipment, and realized the online optimization of the process. The process optimization experiment showed that the oxygen recovery rate of the four-tower structure oxygen generator can reach 50%.
NEWTEK engineers studied molecular sieve pressure swing adsorption (PSA) oxygen production technology, and developed four generations of PSA medical molecular sieve oxygen production equipment, forming a series of products. This series of oxygen production equipment adopts a four-tower structure oxygen production process, and its oxygen yield can reach 40%. Its oxygen production process is realized by a multi-way rotary distribution valve. Therefore, the gas circuit structure is simple, the reliability is high, and the cost is low. However, this type of equipment has a low degree of automation and is more complicated to operate. In order to meet market demand and realize the automation of oxygen production control and further improve quality, we have carried out research on the control system of medical oxygen production equipment.
Control objectives, control objects and process control requirements
Control objectives
Automatic control of the operation process;
Self-diagnosis and self-elimination of faults;
Remote monitoring;
Automatic switching of two machines.
Controlled objects
This control system uses 8m³ medical oxygen generator as the controlled object.
The controlled object consists of circuit system, gas system and water system.
Circuit system
Air compressor operation control;
Freeze dryer operation control;
Pressure pump operation control.
Gas system
(1) Oxygen generator: controller, solenoid valve, cylinder, multi-way rotary distribution valve, gas;
(2) Oxygen buffer tank: controller, solenoid valve, oxygen enters the buffer tank;
(3) Booster pump: controller, solenoid valve, oxygen is sent to the oxygen storage tank through the booster pump;
(4) Oxygen storage tank: controller, solenoid valve, oxygen enters the oxygen storage tank;
(5) Oxygen meter: controller, solenoid valve, gas source is provided to the oxygen meter.
Water system
(1) Air buffer tank drain valve: controller, solenoid valve, drain;
(2) Middle cooling air drain valve: controller, solenoid valve, drain;
(3) Rear cooling air drain valve: controller, solenoid valve, drain.
Process control requirements
Start-up process
(1) Start the freeze dryer.
(2) Start the air compressor. It is prohibited to start it under pressure.
(3) After the air buffer tank reaches a certain pressure, the oxygen generator starts to work. The controller controls the cylinder to cycle according to a certain timing according to the set oxygen production process. The cylinder drives the multi-way rotary distribution valve to work. Under the action of the distribution valve, the air enters the four adsorption towers respectively and produces oxygen through molecular sieve pressure swing adsorption. Requirements: The cylinder operation timing must strictly correspond to the operating status of the multi-way rotary distribution valve, otherwise the program will be confused and the oxygen purity will decrease.
(4) In order to shorten the oxygen production time, the air in each adsorption tower should reach a certain concentration. For this reason, it is required that the oxygen buffer tank solenoid valve lags for a period of time before it operates.
(5) When the oxygen buffer tank reaches a certain pressure, open the drain valve to drain the oxygen.
(6) When the oxygen purity is higher than 90%, turn off the drain valve, open the booster pump solenoid valve and the oxygen storage tank solenoid valve, and high-purity oxygen enters the oxygen storage tank. At this point, the equipment enters normal oxygen production operation state from the startup state.
Operation process
(1) During normal oxygen production, when the pressure of the oxygen storage tank reaches 0.8MPa, turn off the oxygen generator, air compressor, freeze dryer and their corresponding solenoid valves, open the cooling air drain valve in the air compressor for 5 minutes, and release the pressure in the air compressor.
(2) When the pressure of the oxygen storage tank drops to 0.4MPa, restart the freeze dryer, air compressor, oxygen generator and their corresponding solenoid valves according to the startup process.
(3) During operation, each drain valve drains water once every 30 minutes, and each drain lasts about 10 seconds. The three drain valves drain water in turn at a certain interval to avoid excessive pressure drop in the air buffer tank caused by simultaneous draining.
(4) It is required to be able to monitor oxygen purity at any time.
(5) It is required to be able to record the equipment operation time.
Shutdown process
(1) Turn off the oxygen generator host;
(2) Turn off the booster pump and oxygen storage tank solenoid valve and other corresponding solenoid valves;
(3) Turn off the air compressor;
(4) Turn off the freeze dryer;
(5) Open the middle and rear cooling air drain valve, delay for 5 minutes and then turn it off to drain the cooling water and release the residual pressure in the air compressor.
PSA Oxygen Generator For Medical Use
(1) NEWTEK PSA Oxygen Plant control system can make equipment debugging easy, operation simple, safe to use, reliable operation, not only convenient for technicians to install, debug and repair, but also greatly reduce the labor intensity of operators and improve the working environment of operators.
(2) This control system is convenient for process optimization and can further improve the oxygen recovery rate of the equipment.
(3) The programmable controller used in this control system has a serial communication interface, which provides feasible conditions for remote monitoring research; the controller also has the characteristics of multi-user, which can realize the automatic switching function of dual machines.
(4) Since the control requirements and characteristic parameters of PSA series oxygen generators are the same, that is, the control factor k and characteristic parameter p remain unchanged, this control system is also applicable to other models of PSA series.
Products Description
